server.c

// WIN SOCK - TCP Server sample
#include <winsock2.h>

SOCKET init_tcp()
{
	WSADATA wsaData;
	//Check if Operating System support WS2_32.LIB
	int retval = WSAStartup(0x202,   // version number 2.2
							&wsaData // struct contain DLL configuration information
							);
	if (retval != 0)
		return INVALID_SOCKET;
	printf("Server: WSAStartup() is OK.\n");
	//=======================================================
	// TCP socket
	 SOCKET server_socket = socket(AF_INET, // AF_INET = TCP/IP   | PF_INET
								SOCK_STREAM,// SOCK_STREAM = TCP  | SOCK_DGRAM = UDP
								0 // 0 when use AF_INET
								);
	if (server_socket == INVALID_SOCKET)
		return INVALID_SOCKET;
	return server_socket;
}

SOCKET open_tcp(SOCKET server_socket, unsigned short port)
{
	struct sockaddr_in address;
	address.sin_family = AF_INET;
	address.sin_addr.s_addr = INADDR_ANY; //char *ip_address = NULL; inet_addr(ip_address);
	address.sin_port = htons(port);       //Port MUST be in Network Byte Order
	
	int retval = bind(server_socket,            // Connection Type = TCP
					(struct sockaddr*)&address, // IP & Port information
					sizeof(address)             // Size
					);
	if ( retval != 0)
		return INVALID_SOCKET;
	printf("Server: bind() is OK.\n");
	//================================
	retval = listen(server_socket, 5 //Max clients count
						);
	if ( retval == SOCKET_ERROR)
		return INVALID_SOCKET;
	//printf("Server: listen() is OK.\n");
	printf("Server: I'm listening and waiting connection\non port %d, protocol TCP\n", port);
	return server_socket; // (Connection Type  + IP + Port) information
}

int recieve_tcp(SOCKET channel, char Buffer[], int length)
{
	int retval = recv(channel, Buffer, length, 0);
	if (retval == SOCKET_ERROR)
		return SOCKET_ERROR;
	return retval;// number of bytes recieved
}

int send_tcp(SOCKET channel, char Buffer[], int length)
{
	int retval = send(channel, Buffer, length, 0);
	if (retval == SOCKET_ERROR)
		return SOCKET_ERROR;
	return retval;// number of bytes recieved
}

int main()
{
	SOCKET server_socket = init_tcp();
	if (server_socket == INVALID_SOCKET)
	{
		printf("Server: init socket failed: error %d\n", WSAGetLastError());
		return -1;
	}
	//=======================================
	unsigned short port = 5656;
	server_socket = open_tcp(server_socket, port);
	if (server_socket == INVALID_SOCKET)
	{
		printf("Server: open socket failed: error %d\n", WSAGetLastError());
		return -1;
	}
	//=======================================
	
	while (TRUE)
	{
		struct sockaddr_in  client_info;
		int fromlen = sizeof(client_info);
		SOCKET channel = accept(server_socket, (struct sockaddr*)&client_info, &fromlen);
		if (channel != INVALID_SOCKET)
		{
			printf("Server: accept() is OK.\n");
			printf("Server: accepted connection from %s, port %d\n", 
				inet_ntoa(client_info.sin_addr), htons(client_info.sin_port));
		}
		else
			return -1;

		
		char Buffer[128];
		int retval = recieve_tcp(channel, Buffer, sizeof(Buffer));
		if (retval == SOCKET_ERROR)
		{
			printf("Server: recieved from socket failed: error %d\n", WSAGetLastError());
			closesocket(channel);
			continue;
		}
		else if (retval == 0)
		{
			printf("Server: Client closed connection.\n");
			closesocket(channel);
			continue;
		}
		printf("Server: Received %d bytes, data \"%s\" from client\n", retval, Buffer);
		//====================================================
		printf("Server: Echoing the REVERSED data back to client...\n");
		
		/*char Buffer2[128];
		int counter = 127;
		for (int i = 0; i < 128; i++)
		{
			Buffer2[counter--] = Buffer[i];
		}*/
		retval = send_tcp(channel, Buffer, sizeof(Buffer));
		if (retval == SOCKET_ERROR)
			printf("Server: send() failed: error %d\n", WSAGetLastError());
		
		printf("Server: send() is OK.\n");
		//========================================================
		closesocket(channel);
		printf("Server: I'm waiting more connection, try running the client\n");
	}
	return 0;
}